1. Field of the Invention
This invention relates to resource allocation within a computer or other network. More particularly, the present invention relates to the allocation of DSP Resources in a Digital Communications Network.
2. Description of the Related Art
FIG. 1 generally depicts a digital network adapted to transport voice, data and other information. The network includes a plurality of Customer Premises Equipment nodes 100, 108 (hereinafter “CPE nodes”), framer modules 101, 107, Network Interface Systems 102, 106 (hereinafter “NISs”), DPS resources 103, 105 within each of the NISs, and network 104.
When a communication connection is requested from CPE node 100 to CPE node 108 the signal first travels from the CPE node 100 to framer module 101 over digital T1 carriers 110, 120. Before being transmitted over T1 carriers 110, 120, the signal from CPE node 108 is sampled and converted to a digital signal. A common sampling rate to convert the analog signal to digital is 8000 samples per second, with each digital sample represented by 8 bits of data. Thus, the data rate of the new digital signal is: 8000 samples/sec×8 bits=64,000 bits/sec. This technique is known as Pulse Code Modulation (hereinafter “PCM”) and is used extensively throughout the backbone of the modern telephone system.
Although no international standard has been adopted, the T1 carrier is one method of PCM used throughout North America and Japan. The T1 carrier is comprised of 24 channels of digital data multiplexed together. As shown in FIG. 2, digitally sampled data from each of the 24 channels are packaged into successive frames of 8 bits/channel×24 channels+an additional framing bit 210=193 bits. Outside of North America and Japan a similar standard known as E1, is commonly implemented. E1 operates in a manner similar to T1 except that it uses 32 8-bit data samples (i.e., 32 channels) instead of 24.
After the signal has been sampled, converted to a digital signal and transmitted over a T1 carrier 110, as described above, it is then transferred to a framer module 101. The framer module 101 serializes the digital data from the plurality of T1 carriers 110 into a bit stream which is sent to NIS 102. An example of a known framer module is a Rockwell™ BT8370. In the NIS 102 the digital data samples are packaged according to the protocol used in network 104 (e.g., ATM). Additionally, although PCM by itself provides for a data compression rate of 8:1, it is often desirable to further compress the digital PCM data at NIS 102 in order to save bandwidth over the network. This can be accomplished using Digital Signal Processing (hereinafter “DSP”) resource blocks 103, 105 within NIS 102. For example, if the 64,000 bits/second PCM signal is further compressed by DSP resource 103 at a compression ratio of 16:1 the resulting digital signal will be transmitted at 4,000 bits/second. This represents a significant reduction in required bandwidth across network 104 to transmit the same underlying signal. Such compression techniques are particularly useful in networks which are heavily loaded with network traffic. Examples of compression algorithms known in the art include the International Telegraph Union (hereinafter “ITU’) standards G.711, G.726, G.729-A, G.729, and G.728.
However, there is a tradeoff between bandwidth savings over network 104 and the implementation of costly DSP resources 103 in NIS 102. In general, the higher the compression ratio required by the compression algorithm, the more DSP resources 103 are used up processing the compression request over a given period of time. Thus, referring to the table in FIG. 3, while a single DSP resource can process 16 channels of data if no compression is used (i.e., in baseline PCM mode), it can only process 5 channels if data is compressed at 2:1, and only 2 channels if the PCM signal is compressed at 8:1.
This is because the DSP resource has a limited amount of time in which to compress the data within a T1 frame before it must move on to the next frame of data. Referring to FIG. 4, ‘T’ represents the maximum amount of time that a DSP resource may spend compressing data from a frame before it must move on to the next successive frame (i.e., the data from frame 1 must be compressed before frame 2 arrives). While a single DSP resource can process 16 T1 channels per unit of time ‘T’ in baseline PCM mode (i.e., each channel requiring approximately ‘T’/16 to process), the same DSP resource can only process one T1 channel per the same unit of time ‘T’ running at a compression ratio of 16:1. Thus, the chosen compression ratio will have a significant impact on DSP resource usage.
Following compression, the data samples are delivered through network 104 to NIS 106, where the data is decompressed and passed on to framer module 107. Framer module 107 reconstructs the original T1 signal which it transfers to CPE 108 over a T1 carrier 120. The system is bi-directional to ensure 2-way communication.
The management of the DSP resources in prior systems occurs without regard to whether the DSP resources are depleted. In other words, when multiple calls are received from the CPEs 100, the NIS 102 may have its DSP resources 103 consumed quickly. Once all DSP resources 103 in NIS 102 are allocated, any attempt to open a new communication channel through NIS 102 will result in a busy signal. What is needed is a DSP resource allocation system to ensure that there are always enough DSP resources 103 available in NIS 102 to process the incoming data by reserving enough DSP resources to process all idle T1 channels in PCM mode. In sum, a scheme for managing the DSP resources 103 in NIS 402 in order to reduce the possibility that a call request will be rejected is needed.